The present invention relates to an improvement in skis used on snowmobiles or other vehicles to facilitate forward movement and steering. More specifically, to a ski which is constructed entirely from Ultra High Molecular Weight Polyethylene (UHMW), as one piece including the attachment saddle which facilitates the attachment of a ski to the front end of a typical snowmobile.
Typical snowmobiles are powered by a front mounted engine attached to a rear endless track system. The track on conventional snowmobiles is suspended using springs and gas powered shocks to absorb bumps and aid in control and handling of the snowmobile. These snowmobiles are typically supplied with two skis attached to a rider operated steering system. The skis are placed in front of the track system and are, thus, the first part of the vehicle to meet obstacles such as rocks, logs and bumps. Different manufacturers have developed and utilized several different means of adding travel to each individual ski system. These systems range from a wishbone type suspension to an upright spring and dampener type system.
The classic, or conventional, snowmobile ski is constructed of metal and attaches to the steering system mechanism at a point near the middle of the ski. These skis are typically curved upward at the forward portion which allows the ski to ride over obstacles. The curved portion also aids the ski in traveling through snow conditions ranging from deep powder snow to slush and ice.
A stiff loop, made of metal rods, is typically attached to the front portion of the ski near the top of the front curved section. Some skis have used a piece of angle iron or bracketing to increase the strength of the loop. This rod or loop is then attached in a circular fashion back towards the center portion of the ski. The loops have several purposes the first of which is to strengthen the ski. The loops also act as a continuation of the curved portion of the ski and, thus, enhances the skis ability to handle bumps, moguls or obstacles. These loops have also evolved into handles to aid moving the snowmobile or picking up the front for a variety of reasons.
The metal ski has been standard for many years, but recently the industry has begun adopting skis made of metal bridges, reinforcements and plastic portions. This plastic may be of a type such as a Ultra High Molecular Weight Polyethylene (UHMW) or (UHMW-PE) plastic. This type of ski has been developed to overcome some of the disadvantages of the metal ski. One of these disadvantages has been that metal skis are unyielding and thus, subject to dents and bends as the ski is used in normal operation. These bends and dents eventually lead to a drop in performance of the ski and often necessitate the replacement of the ski. The use of flexible and resilient plastics has resulted in skis that are durable and able to withstand impacts that would have damaged conventional metal skis. These skis, however, are made with metal bridges, saddles or supports that result in a ski resilient at its edges, and is overall rigid. The problem with a ski that is overall rigid is that when the tip of the ski encounters a bump or obstacle the ski will follow this bump or move this results in the base of the ski losing contact with the ground or snow which substantially affects the rider's ability to control the vehicle as it will tend to dart from side to side as the ski loses contact with the ground.
U.S. Pat. No. 5,040,818 issued to Metheny on Aug. 20, 1991 and U.S. Pat. No. 5,145,201 issued to Metheny on Sep. 8, 1992, a continuation in part issuing from the 818 patent generally discloses one of the current plastic and metal skis. This ski has a formed plastic base with a metal bridge and saddle top. The front tip of the ski in one embodiment is equipped with a solid loop and upper bridge which holds the front of the ski in a curved and rigid form. In this embodiment the ski is substantially rigid and thus, suffers from the same handling characteristics as the metal ski in bumps. A second embodiment of this ski uses a rigid rod of adjustable length which may used to vary the upward curvature of the ski as the rod is lengthened or shortened. This embodiment has some flexibility however, the flex tends to be behind the rod's connection point and in front of the metal saddle at one point on top of the ski. This tendency to flex at one point, as the rod is solid, results in a ski that flexes too much to the point that it is damaged or broken by severe impacts such as logs or rocks, and thus, can create a dangerous situation for the rider.
Another ski of the plastic variety is shown in U.S. Pat. No. 5,360,220 issued to Simmons on Nov. 1, 1994. This patent discloses a ski having a plastic curved base. The base has a flexible loop attached to the underside of the front and up and over the tip of the ski to a point on the upper base of the ski near the middle. The loop is attached near the middle of the ski in a slidable fashion such that the ski may flex. This configuration works to make the ski somewhat flexible, however, as the ski is pre-curved the flex is not adjustable. The loop acts to evenly distribute the bending and flexing of the ski over a large area. Although, this works to alleviate the problems of flex in one point, and thus, prevents breakage this design is not adjustable to a given rider's size or taste. The ski operates at a preset flex within certain limits. Thus, a rider may still experience problems in bumps with darting as the ski may be too soft for a large rider and thus, flex to a point where the rear portion of the ski leaves the ground and reduces a rider's control of the sled.
From this discussion, it can be seen that it is desirable to supply a ski that works to absorb bumps during riding. It is also desirable to make this ski adjustable to riders of a given weight and different riding styles. Further, it is necessary that this ski be designed to flex evenly throughout its length so that the ski will not buckle under extreme bumps such as ditches, logs and rocks.